1. Field of the Invention
The invention relates to an apparatus for applying a thermoplastic high-polymer material, in particular an adhesive, to a substrate.
2. Description of the Prior Art
The basic construction of such an apparatus can be seen, for example, from German utility model No. 8,534,594 and comprises an application head, a feed passage for the liquefied material in the application head, a nozzle-like outlet opening at the end of the feed passage and a valve arrangement for opening and closing the feed passage or the outlet opening, respectively. Not only the liquefied material is supplied to the application head but at the same time also a gas, generally air which is under pressure, so that the emerging material is atomized by the pressure gas and is applied in the form of a spray curtain or mist to the substrate to be coated.
With the apparatus according to German utility model No. 8,534,594 specific coating patterns can be produced by additional gas, in particular air streams, as are necessary for some purposes. However, in this case the outlet openings for the additional gas streams must be positioned and adjusted very exactly to obtain the desired patterns. Furthermore, it is not readily possible to deviate from a coating or spray pattern once it is set. Finally, a very complicated construction results with the external, additional outlet nozzles for the additional air flow.